A solid oxide fuel cell is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. The SOFC has a ceramic electrolyte. Advantages of this class of fuel cells include high efficiency, long-term stability, fuel flexibility, low emissions, and relatively low cost. The largest disadvantage is the high operating temperature, which results in longer start-up times and mechanical and chemical compatibility issues.
In order to e.g. shorten the start-up times, it has been proposed to use micro-tubular cells instead of planar type cells and to place them in series, thus obtaining micro-tubular SOFCs, which consist of a tubular electrolyte sandwiched between two electrodes, an anode and a cathode. Such micro-tubular SOFCs are e.g. shown in JP 44 07235, wherein short tubular elements are connected in series by means of an interconnector. Such interconnectors are ring-shaped elements receiving, on each side, one end of a short tubular element. An assembly of a plurality of short tubular elements with interconnectors therebetween forms a long tubular fuel cell element.
Such long tubular fuel cell elements also need to be connected in parallel. In order to achieve this, JP 44 07235 suggests connecting two ring-shaped elements together by means of a land.
The interconnector disclosed in JP 44 07235 thus allows the fuel cell elements to be connected in series and in parallel. However, the construction of the fuel cell using such interconnectors is rather cumbersome and time consuming. Furthermore, any play between a short tubular element and an interconnector can be problematic due to the large number of short tubular elements connected in series. Even small plays in a number of connections can quickly accumulate to an inacceptable play over the length of the tubular fuel cell element, thereby endangering the stability of the fuel cell.